Effects of ortho- and para-ring activation on the kinetics of S_NAr reactions of 1-chloro-2-nitro and 1-phenoxy-2-nitrobenzenes with aliphatic amines in acetonitrile

Crampton, M.R.; Emokpae, T.A.; Isanbor, C.; Batsanov, A.S.; Howard, J.A.K.; Mondal, R.

Abstract

Rate constants are reported for reaction of 4-substituted 1-chloro-2,6-dinitrobenzenes 1, 6-substituted 1-chloro-2,4-dinitrobenzenes 2, and some of the corresponding 1-phenoxy derivatives, 3 and 4, with n-butylamine, pyrrolidine and piperidine in acetonitrile as solvent. Values of k1, the rate constant for nucleophilic attack at the 1-position, increase with increasing ring-activation but may be reduced by steric repulsion at the reaction centre which increases in the order Cl < OPh, and n-butylamine < pyrrolidine piperidine. ortho-Substituents may also have adverse steric effects, and those of the trifluoromethyl group are particularly serious. X-ray crystal structures of phenyl 2,4-dinitro-6-trifluoromethylphenyl ether and phenyl 2,6-dinitro-4-trifluoromethylphenyl ether are reported. Base catalysis in the 1-phenoxy derivatives is attributed to rate-limiting proton transfer from the zwitterionic intermediates 6 to base. Values of rate constants for this process decrease with increasing steric congestion at the reaction centre and in the order n-butylamine > pyrrolidine > piperidine.

Citation

Crampton, M., Emokpae, T., Isanbor, C., Batsanov, A., Howard, J., & Mondal, R. (2006). Effects of ortho- and para-ring activation on the kinetics of SNAr reactions of 1-chloro-2-nitro and 1-phenoxy-2-nitrobenzenes with aliphatic amines in acetonitrile. European Journal of Organic Chemistry, 2006(5), 1222-1230. https://doi.org/10.1002/ejoc.200500774

• Journal Article Type: Article
• Online Publication Date: Dec 22, 2005
• Publication Date: Mar 1, 2006
• Deposit Date: Apr 26, 2007
• Journal: European Journal of Organic Chemistry
• Print ISSN: 1434-193X
• Electronic ISSN: 1099-0690
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 2006
• Issue: 5
• Pages: 1222-1230
• DOI: https://doi.org/10.1002/ejoc.200500774
• Keywords: Kinetics, Nucleophilic aromatic substitution, Steric hindrance, Substituent effects.
• Public URL: https://durham-repository.worktribe.com/output/1544217